What system is an upgrade of the Force XXI Battle Command Brigade and Below or Blue Force Tracker?

The correct choice is the Joint Battle Command - Platform (JBC-P), which represents an advancement over the Force XXI Battle Command Brigade and Below (FBCB2), commonly referred to as Blue Force Tracker. JBC-P incorporates new technologies and capabilities designed to enhance situational awareness and the effectiveness of command and control in military operations.

JBC-P integrates advanced features such as improved user interfaces, enhanced mapping capabilities, and better interoperability with various systems and platforms. This upgrade ensures that military personnel can effectively share operational information in real time, thereby improving decision-making capabilities on the battlefield.

The other options listed refer to different systems or concepts that do not directly build upon the capabilities offered by FBCB2. For example, ATN (Advanced Tactical Network) may involve communication technologies, while IFS (Integrated Force Structure) is more about organizational frameworks. POR-B (Projected Operational Requirement - Block) focuses on future capabilities and requirements, which do not signify an immediate upgrade to the Blue Force Tracker system. Thus, JBC-P is distinctly positioned as the technological advancement meant to replace and enhance the functionalities of the original Blue Force Tracker.